If something "out there" was at a distance close enough to have received our radio transmissions, e.g., 75 years ago, and then arrived by now (let alone 50 years ago), then, unless they had the ability to travel faster than the speed of light, they would've already been close enough to observe our planet and its activities in enough detail to determine whether or not our planet would host their kind, long before our radio transmissions.

Use logic.